The focus of the proposed research is to understand the neuroendocrine mechanisms of reproductive communication in the green treefrog (Hyla cinerea). The project will, first, examine the calling behavior of hormonally manipulated males. Hormones suspected to influence calling behavior such as arginine vasotocin (AVT), neuropeptide Y (NPY) and gonadotropin-releasing hormone (GnRH) will be administered via intraperitoneal injection and androgen influences will be examined using receptor blockers and castration. Second, animals with different behavioral patterns will be examined for differences in neurohistology. Neuropeptide systems such as AVT, NPY and GnRH will be examined in addition to catecholamine systems using immunohistological techniques. Third, the effect of the hormone manipulations described above, on the electrophysiological response of auditory nuclei will be investigated. Extracellular mulitcell recordings will be used to test auditory thresholds of manipulated males. Understanding basic neurobiological processes in non-mammalian organisms, such as amphibians, that retain most of the aspects of the same systems in mammals can provide a simplified model for clinical disorders and treatments.